1. Field of the Invention
The present invention relates to a fuel cell and an electronic apparatus on which the fuel cell can be mounted.
2. Description of the Related Art
A fuel cell is a focus of attention as a new energy source because the fuel cell has a higher power generation efficiency than that of a conventional power generation system and an emitted product caused in power generation is clean.
While there are developed various types of fuel cells, a polymer electrolyte fuel cell is suitable for a small electronic apparatus, in particular, a portable electronic apparatus used while being carried.
This is because the polymer electrolyte fuel cell has an advantage in that the polymer electrolyte fuel cell can be used at temperature close to room temperature and includes an electrolyte which is solid instead of being liquid, so the polymer electrolyte fuel cell can easily be carried.
The polymer electrolyte fuel cell basically includes a polymer electrolyte membrane having proton conductivity and a pair of electrodes arranged on both surfaces of the polymer electrolyte membrane. Each of the electrodes includes a catalyst layer mainly including platinum or a platinum group metal catalyst and a gas diffusion electrode formed on an outer surface of the catalyst layer and functioning to feed a gas and to collect electricity. A structure obtained by integrating the pair of electrodes and the polymer electrolyte membrane is called a membrane electrode assembly (hereinafter referred to as MEA). A fuel (hydrogen) is supplied to one of the electrodes and an oxidizer (oxygen) is supplied to the other of the electrodes, thereby performing power generation. Of the electrodes, the electrode to which the oxidizer is supplied is called an oxidizer electrode and the electrode to which the fuel is supplied is called a fuel electrode.
In the fuel electrode, due to a function of a catalyst, protons and electrons are generated from the supplied hydrogen. The protons move from the fuel electrode to the oxidizer electrode through the polymer electrolyte membrane. Further, the electrons move from the fuel electrode to the oxidizer electrode through an external load. In this process, electricity is obtained. On the other hand, in the oxidizer electrode, due to a function of the catalyst, from the protons and the electrons which are moved to the oxidizer electrode as described above and the supplied oxygen, water is generated.
Along with a demand for further downsizing of the electronic apparatus, downsizing of the fuel cell itself is becoming a more important object. That is, there is a demand for improvement in power generation efficiency of a fuel cell by generating a larger amount of electricity by a fuel cell having a smaller power generation area and efficiently taking out the electricity. In order to meet the demand, an attempt has been made in which a uniform pressure is applied to the fuel cell and a contact resistance between components of the fuel cell is reduced, thereby reducing electricity which is wastefully consumed.
Japanese Patent Application Laid-Open No. 2005-310583 proposes a fuel cell having a structure in which the fuel cell which is thin and flexible is wound around a core in a scroll shape and a winding end thereof is fixed by a fixing material. In this manner, by applying a pressure in a laminating direction of the fuel cell, an attempt is made to reduce a contact resistance between components of the fuel cell so that a power generation efficiency is improved.
Further, Japanese Patent Application Laid-Open No. 2004-214040 discloses a fuel cell having a structure in which components of the fuel cell is clamped by a screw in a laminating direction thereof, thereby reducing a contact resistance between the components to increase an output of the fuel cell.
However, the structures of the fuel cells according to the above-mentioned conventional techniques are not necessarily satisfactory for achieving application of a uniform pressure, further downsizing, and facilitation of an operation at a time of assembling the fuel cell.
For example, with the fuel cell according to Japanese Patent Application Laid-Open No. 2005-310583, there is a problem with downsizing of the fuel cell because the fuel cell is wound around the core in the scroll shape, so an additional member such as the fixing material for fixing the winding end is needed. Further, there is caused an operational burden at the time of assembling a cell unit such as an operation for winding the fuel cell in the scroll shape. It is difficult to apply a uniform pressure to a beginning portion of winding close to a central portion and a winding end portion close to a peripheral portion.
Further, with the fuel cell according to Japanese Patent Application Laid-Open No. 2004-214040, in order to reduce the contact resistance between the components by deflecting the presser members for applying the pressure in the vicinity of a central portion of the presser members toward the MEA side, the additional member such as a screw for fixing is required and a uniform pressure application is difficult.